This invention relates to a motion picture camera and specifically to a motion picture camera having a capping shutter which provides for a light-tight covering of the motion picture film during a single frame exposure or time exposures.
From DE 44 18 471 A1, a motion picture camera for exposure of a motion picture film is known, whereby the unexposed film fed from a film cassette intermittently passes a gate by means of a film transport mechanism, which is disposed in the focal plane of a camera lens. Between the camera lens and the gate, a rotating shutter disk, from which a shutter opening is cut out (i.e., the shutter disk is not a complete disk in that a section of it is missing) and which is alternatively connected via a gear with the film transport mechanism or is driven by a shutter motor, is provided.
During transport of the film from one frame to be exposed to the next, the optical path from the camera lens to the gate is covered by a shutter disk. When the next frame has reached a predetermined position in front of the gate, the optical path is cleared for exposure of the frame by the opening of the shutter disk. By means of a mirrored surface on the shutter disk, the optical path through the camera lens can be diverted during transport of the film, when the gate is covered by the shutter disk, to a viewfinder, a video assist, or the like. The rotating shutter disk which is inclined relative to the optical axis of the camera lens, must have a sufficient diameter such that it completely covers the gate. Moreover, the rotating shutter disk body when rotated must cover the optical axis for a sufficient time to allow for the transport phase of the film.
The rotating shutter disk design, in particular with time exposures, does not prevent roaming light from entering the area of the gate and reaching the film, resulting in faulty film exposures.
To preclude such faulty exposures, it is known in time exposures, such as single-frame exposures, to provide an additional covering shutter, referred to herein as a capping shutter, in front of the camera lens, which is closed between the single-frame exposures, therefore suppressing any beam entry into the camera lens and thus to the gate or the motion picture film. Such a capping shutter may consist, for example, of an iris shutter with multiple lamellae, which are moved by means of a lifting magnet. Not until immediately before the end of a dark phase or a pause in the exposure is this capping shutter opened by means of the lifting magnet clearing the optical path through the camera lens to the gate when the rotating shutter disk is appropriately positioned.
Such a capping shutter has, however, considerable weight, which is disposed in an disadvantageous position relative to the center of gravity of the motion picture camera because of the placement of the capping shutter in front of the camera lens. During operation, the relatively large and mechanically moving parts of the capping shutter cause vibration during exposure of the frame, such that there is a risk of unsharp blurry exposure.
In addition, there is for the cameraman no possibility of observing the image through the viewer or the video assist between the shooting of single frames since the capping shutter blocks the entire optical path through the camera lens and thus its diversion by means of the mirrored surface on the rotating shutter disk.
Moreover, such a capping shutter demands high outlays for construction and is thus expensive.